Java 如何从最后一个迭代到第一个ArrayList？
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How to iterate from last to first an ArrayList?
提问by Ricardo Sanchez
I wonder if is possible to iterate from last to the first element in an ArrayList, if so how? The reason is because I need to remove the last element added to the list
我想知道是否可以从 ArrayList 中的最后一个元素迭代到第一个元素，如果可以，如何？原因是因为我需要删除添加到列表中的最后一个元素
采纳答案by dasblinkenlight
While you can always iterate your ArrayListusing an index, like this
虽然您始终可以ArrayList像这样使用索引进行迭代
List<String> myList = new ArrayList<String>();
... add code to populate the list with some data...
for (int i = myList.size() - 1 ; i >= 0 ; i--) {
if (myList.get(i).equals("delete me")) {
myList.remove(i);
}
}
you would be better off using a ListIterator<T>for the purpose of deleting items from your ArrayList:
您最好使用 aListIterator<T>来从您的 中删除项目ArrayList：
ListIterator<String> listIter = myList.listIterator();
while (listIter.hasNext()) {
if (listIter.next().equals("delete me")) {
listIter.remove();
}
}
List iterators can be used to iterate your list backwards, too -- like this:
列表迭代器也可用于向后迭代您的列表——就像这样：
ListIterator<String> listIter = myList.listIterator(myList.size());
while (listIter.hasPrevious()) {
String prev = listIter.previous();
// Do something with prev here
}
The initial index of the iterator should be equal to the index of the last element + 1. As the docssay: "An initial call to previouswould return the element with the specified index minus one."
迭代器的初始索引应该等于最后一个元素的索引 + 1。正如文档所说：“初始调用previous将返回具有指定索引减一的元素。”
回答by Dom
If you need to just remove the last element of an array list, you could just do:
如果您只需要删除数组列表的最后一个元素，您可以这样做：
arrayList.remove(arrayList.size()-1);
If you wanted to remove all elements from back to front, you could use this for loop:
如果你想从后到前删除所有元素，你可以使用这个 for 循环：
for(int i = arraList.size()-1; i >= 0; i--)
{
arrayList.remove(i);
}
For more infomation on Array Lists, you can go here: http://www.tutorialspoint.com/java/java_arraylist_class.htm
有关数组列表的更多信息，您可以访问这里：http: //www.tutorialspoint.com/java/java_arraylist_class.htm
Hope this helps.
希望这可以帮助。
回答by Michael Easter
Here is one way to do it (your reason why is a separate question):
这是一种方法（您的原因是一个单独的问题）：
import java.util.*;
List<String> list = new ArrayList<String>();
list.add("a");
list.add("b");
list.add("c");
ListIterator<String> iter = list.listIterator(list.size());
while (iter.hasPrevious()) {
String s = iter.previous();
System.out.println(s);
}
回答by melc
ArrayList aList = new ArrayList();
aList.add(1);
aList.add(2);
aList.add(3);
Collections.reverse(aList);
Iterator iter = aList.iterator();
while(iter.hasNext()){
iter.next();
iter.remove();//remove an element
break;//break from the loop or something else
}
回答by jdev
List<String> names = ....
int count= names.getSize();
Iterator<String> i = names.iterator();
while (i.hasNext()) {
String s = i.next(); // must be called before you can call i.remove()
// Do something
if (count==1)
i.remove();
count--;
}
